Nemotron 3 Ultra 550B A55B
NVIDIA · 2026-06-04 · 560.5B parameters
Nemotron 3 Ultra 550B A55B is NVIDIA's open-weight, post-trained frontier reasoning model in the 550-billion-parameter class, with a publicly reported 55 billion active parameters per token, released on June 4, 2026. It uses a hybrid LatentMoE architecture combining Mamba-2, MoE, and attention layers with MTP, supports configurable reasoning, and has a documented maximum context of 1,048,576 tokens even though the checkpoint configuration defaults to 262,144. NVIDIA pre-trained it with an NVFP4 recipe and post-trained it with SFT, reinforcement learning, and MOPD for coding, math, instruction following, tool use, and long-context agentic workflows; the BF16 checkpoint is released under OpenMDW-1.1.